The present invention generally relates to magnetic resonance imaging (MRI) systems, and more particularly to MRI systems that include acoustically damped gradient coils.
Typical MRI devices include a magnet assembly that generates a magnetic field in the presence of at least one gradient coil assembly configured to produce magnetic field gradients in response to the magnetic field. The gradient coil assembly includes a plurality of coils that typically produce three magnetic field gradients, each of which is oriented in a perpendicular fashion with respect to one other (e.g., along x, y, and z-axes). MRI procedures are further discussed in U.S. Pat. No. 6,584,337, entitled “Method and System for Extended Volume Imaging Using MRI,” which is hereby incorporated by reference in its entirety.
During an MRI procedure, an electromagnetic force is exerted on the gradient coil causing the gradient coil to vibrate. The vibration of the gradient coil causes vibratory acoustic energy. Often, the vibratory acoustic energy is translated throughout the MRI device, thereby producing acoustic noise. The acoustic noise caused by the vibration of the gradient coil may exceed the ambient background noise. The excessive noise generated during an MRI procedure may be unsettling to patients and irritating to physicians and x-ray technicians.
In order to alleviate the amount of acoustic noise generated by the vibration of gradient coils, rubber dampers have been positioned between a gradient coil and a bobbin that supports the gradient coil. The rubber dampers act to decrease the transmission of acoustic energy from the gradient coil to the bobbin. Further, U.S. Pat. No. 5,345,177, entitled “Magnetic Resonance Imaging Apparatus Having Vibration Damping Means on Gradient Coil” (the '177 patent), discloses a vibration damping means disposed between the gradient coil assembly and a structure that supports the gradient coil.
Additionally, U.S. Pat. No. 4,954,781, entitled “Nuclear Magnetic Resonance Imaging Apparatus with Reduced Acoustic Noise” (the '781 patent) discloses a “sandwich structure” that is located between a body to be examined and a main magnet. The sandwich structure includes a viscoelastic layer sandwiched by first and second sandwiching members.
Further, U.S. Pat. No. 6,107,799, entitled “Noise Reduction Arrangement for a Magnetic Resonance Tomography Apparatus” (the '799 patent) discloses at least one noise-reducing pillow positioned between a gradient coil and a magnet assembly.
Despite the efforts to reduce the amount of acoustic noise within MRI systems described above, many MRI systems still produce levels of acoustic noise that are unsettling to patients and technicians alike. Thus, a need exists for a magnetic resonance imaging system and method that produces less acoustic noise.